UHF radio control for submarines (openLRS, LoRa, FSK etc. on 458Mhz and 433Mhz )

Another test of the LoRa system in my Turkish Nordenfelt model. I am quite happy with the system now and I will use it as my control system "of choice" from now on. (With openLRS used occasionally.)

It has quite high latency but this is OK for submarine models, I think. I like the telemetry (battery voltage is so useful if you are using Lipos) and the failsafes (set in software.) The range (including submerged) is very adequate.

The latest version of the software continues to send telemetry every 10 seconds even if the TX is off. This does perhaps enable lost model direction finding and location (in addition to ultrasonic Pinger use) with my foldable Yagi antenna used some months ago:



The software (Current versions LoRa-Rhead-RX-3.4  & Lora-Rhead-TX-2.7) is here:

https://github.com/rdforrest/LoRa-TX-RX-Test-458MHz








Dived with just the funnel showing!



Dived with just the funnel showing! (Typically murky water)



The TX setup installed in a (fairly roomy) 3D printed box:
The oLED display cycles through the three telemetry values. (This shows the RSSI)



This shows battery voltage:






Two TX/RX sets of equipment (fairly easy to assemble by the informed DIY builder) They all use the Adafruit RFM96W breakout board which is easier to connect to than a bare chip and has level convertors for the 5v used in the Arduino Nano:



Perhaps not the most exciting set of videos but they show the range you can expect together with demonstrations of diving etc.

https://youtu.be/1oW9hinyQcs

https://youtu.be/EuwLlZFAwpA

https://youtu.be/5Jb61F0cMoo

https://youtu.be/q9l2JEAQ9Qo

https://youtu.be/XgTsew0UZwo

So, my update on the ImmersionRC ezuhf equipment...

not worth the bother for me.

I spent the weekend of septermber 4th & 5th 1250 miles from home at a Mare Island Fun Run in "lovely" San Francisco. I took 3 submarines with me, my trusty Norbert Bruggen Delta, a Small World Models 1/96 scale Blueback (1970s era US diesel sub) and a 1/32 scale 1903 Holland. the holland and blueback were using the FrSky 915mhz equipment, and the delta was using the ezuhf equipment.

all three ran equally well in identical conditions.


One thing that was very interesting to me.

One of the local Mare Island club members was using a FrSky qX7 transmitter with a 75mhz futaba module.

https://store.flytron.com/products/turnigy-x9-futaba-module-adapter-v3

he simply wired up an old 75mhz antenna to the appropriate pin on the module, plugged the module into the adapter, plugged the adapter into the socket on the back of the transmitter, and made a bracket to mount the antenna on the transmitter, he set the protocol for the module to PPM, and everything ran as expected.

Very interesting observation Tim.

Does that mean that the Futaba modules use a standard PPM signal as input?

In which case anyone with  a 75mHz or 40 Mhz* module could plug it into the trainer plug of any TX?

Could be very useful for a lot of folks.

David

* for the UK. When last I looked they were expensive and hard to find.

david f wrote:Very interesting observation Tim.

Does that mean that the Futaba modules use a standard PPM signal as input?

In which case anyone with  a 75mHz or 40 Mhz* module could plug it into the trainer plug of any TX?

Could be very useful for a lot of folks.

David

* for the UK. When last I looked they were expensive and hard to find.

David, yes, the protocol selected when using the 75mhz (or 40mhz) modules would be ppm...  and the use of a trainer port instead might add additional "needs"  (some trainer ports invert the signal, and some require the use of a "trainer switch" to indicate who has control of the rf deck, student or instructor)...

and yes, here in the states, the 75mhz modules are impossible to find, and expensive...  but for someone that already has a drawer full of them...

I joined this forum after reading about your issues using openlrs. im probably one of the handful of people that originally used openlrs on 458mhz. Openlrs has potential for very long range and signal penetration but it has to be configured for it, the main issues i could see you having is

1. antennas, the stock openlrs antennas are rubbish and are only useful for indoor testing. make a 1/4 wave dipole using some wire or coax. you need one for both the transmitter and receiver. 433mhz antennas wont be correctly tuned, so you need an antenna that is slightly shorter to compensate for the higher frequency.

2. Air data rate, openlrs has 2 data rates in the settings, one is for the serial port and one is for the transmission rate. out the box this is set quite high as its also used for a telemetry link but since your not using a flight control system you dont need the bandwidth or the low latency so you should drop the transmission rate down to 9600 or 4800 and also reduce the number of channels to 4+4 (4 high resolution channels + 4 low resolution channels) to minimize data usage minimizing the latency. by reducing the transmission rate you more than double the range and it shouldn't effect your FRSKY D based telemetry since it doesn't use much data.

you should also look at the Beacon function of the openlrs recevier, basically if it doesn't receive a packet from the handset it will start transmitting a tone on fixed frequency lowering the power level with each pulse so you can use the RF signal to tell if your getting closer or not. this was tested to 100+ miles in open air using a baufang radio, but it should still work to a decent depth, as the signal required is much weaker than needed for a data link.


openlrs has something called channel relay mode so you can use the servo pins to directly turn signals off and on, so you can just use a opto-isolated relay to run systems.